Ultraconserved non-coding DNA within insect phyla

Abstract

Presence of ultra-conserved sequence elements in vertebrate enhancers suggest that transcription factor regulatory interactions are shared across phylogenetically diverse species. To date evidence for similarly conserved elements among evolutionarily distant insects such as flies, mosquitos, ants and bees, has been elusive. This study has taken advantage of the availability of the assembled genomic sequence of these insects to explore the presence of ultraconserved sequence elements in these phylogenetic groups. To investigate the integrity of fly regulatory sequences across ~100 million years of evolutionary divergence from the fruitfly Drosophila melanogaster, we compared Drosophila non-coding sequences to those of Ceratitis capitata, the Mediterranean fruit fly and Musca domestica, the domestic housefly. Using various alignment techniques, Blastn, Clustal, Blat, EvoPrinter and Needle, we show that many of the conserved sequence blocks (CSBs) that constitute Drosophila cis-regulatory DNA, recognized by EvoPrinter alignment protocols, are also conserved in Ceratitis and Musca. We term the sequence elements shared among these species ultraconserved CSBs (uCSBs). The position of the uCSBs with respect to flanking genes is also conserved. The results suggest that CSBs represent the point of interaction of multiple trans-regulators whose functions and interactions are conserved across divergent genera. Blastn alignments also detect putative cis-regulatory sequences shared among evolutionarily distant mosquitos Anopheles gambiae and Culex pipiens and Aedes aegypti. We have also identified conserved sequences shared among bee species. Side by side comparison of bee and ant EvoPrints identify uCSBs shared between the two taxa, as well as more poorly conserved CSBs in either one or the other taxon but not in both. Analysis of uCSBs in dipterans, mosquitos and bees will lead to a greater understanding of their evolutionary origin and the function of their conserved sequences.